to use or not to use a Rear Sway bar - that is the

#21

[quote=“Steve D” post=56294][quote=“Ranger” post=56269]Having a bar with only a couple discreet adjustment points is a problem. Some bars are continuously adjustable. I can feel 2mm of adjustment and 4mm is very noticeable.

If I can feel 2mm, anyone can.[/quote]Can you feel 2 mm with someone else adjusting the bar and not telling you if/what change they made?

I’ll bet you the entry fee for Friday test day at CMP that you can’t tell 4 mm. :laugh:[/quote]

2mm is iffy. Because the test is not double-blind, it’s hard to trust the result. But 4mm is obvious. Let me get out of the red for vacation time at work, and we’ll do that test. I’d hate to take your money tho, it was kind of you to buy us beer at RA.

[quote=“ilateapex” post=56283]Also keep in mind that the two sides do not have to be adjusted the same. As long as there is no pre-load one side can be in the center hole and one side in the last hole. Or if like Rangers’s one side 10 mm and one side 0 mm.
[/quote]
That’s a clever approach to getting smaller adjustment increments.

#22

[quote=“Ranger” post=56297][quote=“ilateapex” post=56283]Also keep in mind that the two sides do not have to be adjusted the same. As long as there is no pre-load one side can be in the center hole and one side in the last hole. Or if like Rangers’s one side 10 mm and one side 0 mm.
[/quote]
That’s a clever approach to getting smaller adjustment increments.[/quote]P.S. My wager was based on a single 4 mm adjustment, not 4 mm to both sides. I’ve read some very pointy-headed arguments about whether it matters which side you adjust on a sway bar, but given the fact that the only thing that effects a change is the average of the length of the legs on a U-shaped sway bar…

#23

Right we’re on the same page. Let me paraphrase for the sake of being pedantic: the balance you want isn’t about how the car feels per-say, but about how early you can go to throttle. Sometimes, it might feel ugly, but it’s actually getting around faster because throttle applications over-all are earlier.

Yeah, but this is why I am calling this test void. My suspension is too random and unprepared - this is my next phase of the build. I also don’t have the power and torque (or gearing) I need to validate the findings for the overall SE30 community. However, my findings as they relate to the E30 chassis is concerned; this is a viable tuning option/alternative.

Hehehe exactly.

As an aside, my informal survey of the guys at BWRP last weekend proved a lot of variation… One didn’t even turn up with a rear bar and ran in the 2:10’s, one had it on as stiff as he could and ran 2:10’s, one didn’t even know what it was and ran in the 2:10’s, another had it set up by someone else and didn’t know either and ran 2:10’s in the race and 2:09 in Qually. So… my conclusions are that Ranger and chaos theory for the amateur racer has more weight than any research I have done thus far :wink:

#24

[quote=“Steve D” post=56299][quote=“Ranger” post=56297][quote=“ilateapex” post=56283]Also keep in mind that the two sides do not have to be adjusted the same. As long as there is no pre-load one side can be in the center hole and one side in the last hole. Or if like Rangers’s one side 10 mm and one side 0 mm.
[/quote]
That’s a clever approach to getting smaller adjustment increments.[/quote]P.S. My wager was based on a single 4 mm adjustment, not 4 mm to both sides. I’ve read some very pointy-headed arguments about whether it matters which side you adjust on a sway bar, but given the fact that the only thing that effects a change is the average of the length of the legs on a U-shaped sway bar…[/quote]
Near as I can figure it shouldn’t matter which side the bar is adjusted on. A sway bar is a basic torsion spring and the variable is the length of the bar between attachment points, not any absolute about exactly where one attachment point is. This assumes that preload stays neutral.

But sometimes there’s subtlties in the real world that throw a monkey wrench into the book learning, so you never know.

#25

I think that picking the correct rear bar is the biggest part. Going to a lighter rear bar made a big difference us and the 16mm bar with five setting gave us the room we needed to get it right.

#26

I’ve been thinking about the rear sway lately. I had a hard time last year with the idea that the new springs would cause oversteer. I was focused on the idea that the roll stiffness with the new springs changed more in front than in the rear. This was because the front springs were changed dramatically, but the rear springs not so much.

But the fact that with the old springs we were very compression limited, both front and rear, changes things. The idea above that the center of roll resistance went forward assumed that we had suspension travel. But with the old springs the front bottomed out on the bumpstops and the rear bottomed out in coilbind. Since we were on the bumpstops at rest in front, the actual front spring rate was crazy high for 10-20mm and then it wouldn’t move further. And in the rear we had what, 1.5" of travel before the old springs bound up? That makes a mess of any attempt to figure out the center of roll resistance before vs. after.

I lifted the front of my car, I dunno, prob 20mm, and now I’ve got prob 3" of available compression in the rear. With the old springs our sway bars didn’t play much because our suspension didn’t compress much. But now the front and rear of my car can compress so the sway bars impact handling now a helova lot more then they did before. That’s a theory that fits the new springs with a change in our sway bar needs. It’s not so much the new springs, it’s the fact that we can now set up our cars such that the suspension can travel a bit.

#27

Running the stock rear sway bar actually is a benefit, but you must have your ride height set correctly for your car and driving style.